Seaplane float



Patented Jan. 22, "1935 UNITED STATES PATENT OFFICE SEAPLANE FLOAT Adolf Beck, Bitterfeld, Germany, assignor to I.

Farbenindustrie Aktiengesellschaft, Frankfort 2 Claims.

The present invention relates to aluminiumbase alloys and is more particularly concerned with aluminium alloys combining excellent mechanical strength properties with a high resistance to corrosion by sea-water and similar agents.

It is well known that the mechanical properties, such as tensile strength, etc., of pure aluminium may be considerably improved by the incorporation of certain quantities of magnesium, and alloys of this kind containing about 10 percent and more of magnesium had many years ago acquired a standing under the name of Magnalium. When, on the other hand, the magnesium content is below about 10 percent, the improvement of the mechanical properties efiected by the presence of magnesium is generally insufficient for constructive purposes. In recent years, however, the exploitation of the alloys of the Magnalium type has been practically abandoned in view of frequent reports that the resistance of the said alloys to corroding agents was but small as compared with aluminium-base alloys of other composition. Notwithstanding, aluminium-base alloys containing exceedingly small percentages of magnesium in combination with silicon or copper have found a wide field of application since the mechanical strength of the alloys in question, which have become known under the name of Duralumine, may be considerably improved by the application of heat treatment. However, the present invention is not concerned with alloys of the Duralumine type, and only contemplates aluminium-base alloys containing at least about 6 percent and more of magnesium.

A recent investigation of the behavior of alloys belonging to the Magnalium type has proved, that the former reports stating an inferior resistance to corrosion are largely due to the fact that the alloys then under examination cointained comparatively large quantities of non-metallic impurities such as nitrides, oxides, and chlorides. I have further ascertained that, when such impurities are studiously avoided, the alloys of the Magnalium type are practically proof against atmospheric corroding influences.- It finally transpired that witha rising magnesium content in these alloys, the resistance to corrosion by sea-water is more and more improved and that with a magnesium content ranging between about 6 and 8 percent, the alloys are already practically proof against sea-water while still remaining well workable by forging, rolling etc. In view of the fact, however, that the mechanical strength of such alloys containing but moderate percentages of magnesium is insufficient for many 00. In Germany August 21, 1930 purposes of construction, I havesought means to improve the mechanical strength of these alloys without forfeiting their high resistance to seawater and their workability.

My investigations have now shown that the incorporation of small quantities of manganese preferably ranging between about .3 and .1 percent in these alloys has the effect of raising the mechanical properties to the desired degree while maintaining their plasticity and without impairing their resistance to corrosion. Furthermore, it has been observed that with these alloys containing between 6 and 8 percent ofmagn'esium and .3 to 1 percent of manganese the loss in mechanical strength caused by a prolonged contact with sea-water, which occurs with all aluminium-base alloys, is particularly small. Thus, their mechanical properties render these alloys useful for a great many constructive purposes where high strength is required, and in which other aluminium alloys either having only excellent mechanical properties, or alloys having only a high resistance to corrosion are unsuitable, since it was impossible hitherto to simultaneously raise both qualities in the necessary degree. The alloys according to the present invention may therefore be successfully employed as'a material for highly stressed parts which are permanently exposed to sea-water, such as floats for sea-planes etc.

The figures given in, the following table demonstrate the improvement in mechanical properties (tensile strength and yield point), obtained by the presence of .5 and 1 percent of manganese, respectively, in extruded alloys according to the present invention.

Composition of Tensile strength Yield point alloy kgsJsq. mms. kgsJsq. mms.

6 perc. magnesiumnn- 28. 5 12. 9

7 pore. magnesium..." 31.5 '13. 4

.Z fifa niii nfia jii 33.4 s. a

8 pore. magnesium".-- 32. 4 13. 6 ft fife nifiti fiaj: 35.0 11.5

i $%$?:II so. 8 19. s

Owing to their comparatively low magnesium contents, the alloys according to the invention lend themselves to forging, rolling and the like processes which, with a magnesium content exceeding about 8 percent become extremely difllcult to perform.

It should be particularly noted that the invention contemplates alloys containing, besides aluminium, only magnesium and manganese, except of course the usual impurities occurring in these metals, the said alloys thus being clearly distinguished from other known aluminium-base alloys containing, besides magnesium and/or manganese, antimony or similar'metals.

I claim:

1. A sea-plane float having that portion exposed to sea-water substantially built of a rolled aluminium base alloy consisting of between about 6.5 and about 7.5 percent of magnesium and between about .3 and .8 percent of manganese, the remainder being aluminium said alloy being substantially unaffected by sea-water.

2. A marine structural part which; in its normal usage, is exposed to sea-water substantially built of an aluminium base alloy consisting of between 6.5 and about 7.5 percent of magnesium and between about .3 and .8 percent 01' manganese, the remainder being aluminium, said alloy being substantially unaffected by sea-water.

ADOLF BECK. 

